焦作煤田煤储层物性特征及控气因素

Coal Reservoir Properties and Coalbed Gas Controlling Factors of Jiaozuo Coalfield

根据以往资料和实验测试结果,研究了焦作煤田主力煤层二1煤层的储层结构、渗透性、吸附性等物性特征及分布规律,采用定性与定量相结合的方式,对煤层含气性的变化规律及控制因素进行了探讨。研究认为:焦作煤田二1煤层微孔含量最高,其次是过渡孔,而大中孔含量要低得多,具有很强的吸附能力和较强的扩散能力,但渗流或层流能力很弱;煤层渗透率较低,且随着埋深的增加而减小,但地质构造对煤层渗透性具有一定的影响,并且研究区内煤层压裂处理渗透性可明显改善;煤层顶、底板岩性为煤层气体提供了良好的保存条件,而有效埋深、断裂构造对本区煤层含气性具有重要的控制作用。随着有效埋深的增加,含气量先是急剧增大,到了一定阶段后,增大趋势变缓,之间具有对数正相关关系;向斜轴部煤层气含量高于两翼,而背斜则呈现相反的趋势;区域大断裂带附近以及多组断裂的交会部位,煤层含气量往往较低。

Based on measures on coal samples and the pore structure, permeability and adsorption of the Ⅱ relative previous data, the property of fracture and 1 coalbed methane reservoir in the Jiaozuo coalfield were systematically studied. The gas-bearing change law and the influence factors on gas-bearing properties were discussed using qualitative and quantitative analyses. The study shows, micropores are the major pore, transitional pores are the second and macropores are far less in the Ⅱ1 coal, thus for the kind of coal, the adsorption capacity is very high, the diffusibility is a little strong, but the capacity of seepage and laminar flow is very weak. The permeability coefficient is low and decreases with the burial depth of the combed, and the permeability also is influenced by the geo-structure and can be improved under hydraulic fracturing. The roof and floor of the Ⅱ1 coalbed provide favorable gas-preservation conditions, and the effective burial depth and faults structure are also the major factors causing gas-bearing change in the Ⅱ1 coal. The effective burial depth and gas-content is in positive correlation. The gas content in the axial part of the syncline is greater than that in the wings, and the relation is the very opposite in the anticlines. The gas content is often low near the regional faults or in the intersection part of the regional faults.